Nature has a review of a book on Aristotle:
Aristotle is considered by many to be the first scientist, although the term postdates him by more than two millennia. In Greece in the fourth century BC, he pioneered the techniques of logic, observation, inquiry and demonstration. These would shape Western philosophical and scientific culture through the Middle Ages and the early modern era, and would influence some aspects of the natural sciences even up to the eighteenth century…
Leroi, an evolutionary developmental biologist, visits the Greek island of Lesvos — where Aristotle made observations of natural phenomena and anatomical structures — and puts his own observations in dialogue with those of the philosopher. It was in the island’s lagoon of Kolpos Kalloni that Aristotle was struck by the anatomy of fish and molluscs, and started trying to account for the function of their parts. Leroi’s vivid descriptions of the elements that inspired Aristotle’s biological doctrines — places, colours, smells, marine landscapes and animals, and local lore — enjoin the reader to grasp them viscerally as well as intellectually.
But it is important to distinguish between natural philosophy and science. I have always thought Francis Bacon was the first scientist due to his, y’know, inventing much of what we consider scientific method. I don’t know the extent to which he codified existing ideas versus creating some sort of novel synthesis?
The history of the scientific method is of course a long gradient. Perhaps it began with another early innovator in scientific methodology was Ibn al-Haytham:
The prevailing wisdom at the time was that we saw what our eyes, themselves, illuminated. Supported by revered thinkers like Euclid and Ptolemy, emission theory stated that sight worked because our eyes emitted rays of light — like flashlights. But this didn’t make sense to Ibn al-Haytham. If light comes from our eyes, why, he wondered, is it painful to look at the sun? This simple realization catapulted him into researching the behavior and properties of light: optics…
But Ibn al-Haytham wasn’t satisfied with elucidating these theories only to himself, he wanted others to see what he had done. The years of solitary work culminated in his Book of Optics, which expounded just as much upon his methods as it did his actual ideas. Anyone who read the book would have instructions on how to repeat every single one of Ibn al-Haytham’s experiments.